Marseille Interpretation

the term "Marseille" is used humorously in part, it could also be called the "Haifa Interpretation" because Asher Peres contributed and he was at the Technion

and also David Mermin at Cornell (Ithaca, NY) has written similar stories about how to interpret QM and has called his stories the "Ithaca Interpretation"

Or it could be called "Princeton" because of B. van Fraasen's contribution, or one could cite Michel Bitbol who is somewhere in France and call it the "French" interpretation. That actually sounds OK and would include the Marseille people.

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Anyway we need a thread that focuses just on the Marseille interpretation of QM and does not get sidetracked. I need some peace and absence of distraction in order to unfold whatever it is this has to tell us.

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The first thing to say is that INTERPRETATION has to do with the STORIES rather than the mathematical notation or "formalism". Two people can use the same or very similar formulations----the same subscripts and the same equations, or almost the same---and interpret them in radically different ways.

when we are discussing interpretation, similarity at the level of symbolic notation is SUPERFICIAL RESEMBLANCE and what is deep is the stories.
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An illustration of this is that the math of Special Rel was developed by a highly respectable Dutchman named Hendrik Lorentz, who unfortunately told the wrong STORIES about it.
One could say Einstein's contribution to Special Rel was an INTERPRETATION of formulas that were already there. He found the right philosophical spin to put on them.

In particular he found that you had to give up the intuitive notion of SIMULTANEITY.

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Simultaneity was deeply rooted in the human mind, for a reason I will discuss, and in order to tell the right stories about the Lorentz transformations you had to give it up-----eradicate, meaning tear out by the roots. Not easy to do. A purely philosophical step, and nevertheless necessary to the development of physics at that junction.

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So we have to be alert to whatever the Marseille Interpretation is asking us to give up. It will be something that seems obvious to us but for which there is no actual concrete evidence.

Smerlak Rovelli, and also
Asher Peres (who, while he may not be saying exactly the same thing, says it very nicely)

Also the Laudisa Rovelli article in the Stanford Encyclopedia sheds some light

First and foremost I want to EXPLICATE----to hear receptively what these voices are saying

In case anyone is new to this, I will get some links

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Oh BTW Rovelli Smerlak says repeatedly what it is we have to give up. It is Einstein's super-realism. This is a deeprooted mistake for which there is no actual evidence----the unstated assumption that there is one preferred account of the facts.

The several QM paradoxes, by now banal, show that the super-realism assumption is an UNREALISTIC EXPECTATION to have about nature.

Nothing in our experience supports the notion that there is one official account of the facts. But some people persist in believing that there should be. I want to try to understand their psychology.

Why the notion that there should be one preferred wavefunction, one bookkeeping device, should be psychologically appealing to some. I think it is the superbeing perspective, which it may be emotionally satisfying to adopt and this may explain the deep-rooted appeal of what is AFAICS unsupported by the experience of empirical science

Here is Rovelli Smerlakhttp://arxiv.org/abs/quant-ph/0604064Relational EPR
Matteo Smerlak, Carlo Rovelli
7 pages
"We argue that EPR-type correlations do not entail any form of "non-locality", when viewed in the context of a relational interpretation of quantum mechanics. The abandonment of strict Einstein realism advocated by this interpretation permits to reconcile quantum mechanics, completeness, (operationally defined) separability, and locality."

Here is Pereshttp://arxiv.org/abs/quant-ph/0310010Einstein, Podolsky, Rosen, and Shannon
Asher Peres
2 pages
"The EPR paradox (1935) is reexamined in the light of Shannon's information theory (1948). The EPR argument did not take into account that the observers' information was localized, like any other physical object."

I see, I'm quite familiar with RQM by now and will just give my own personal perspective here. There are two analogies that drive it, galillean and special relativity, which both say that different observer descriptions on something particular might not agree, that the valid statements are "relational".

What is critically missing from RQM is synchronisation. Due to this RQM is IMO best understood as an account of why the formalism of QM, which escapes any consistent onthological interpretation, even as relational data, is still consistent epistemologicaly for all observers.

...formalism of QM which escapes any consistent onthological interpretation... is still consistent epistemologicaly...

Asher Peres put this nicely in "EPR Shannon" he said

Quantum states are not physical objects: they exist only in our imagination.

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But as to what is really missing, or rather what has been EJECTED, Rovelli Smerlak tell us over and over what excess baggage they think we have to throw out: they refer to it as "EINSTEIN'S STRICT REALISM" and words to that effect---some single-minded insistence on one preferred account of the facts.

Well, the question is, are we done if we keep saying let's throw away the excess baggage and take quantum states as epistemological.

Imagine we have three systems A, B and C. A and B meassure C. Now if A meassures what B has meassured with respect to C it will find it consistent with it's own meassurement of C. So will B with respect to A. What they will find if the epistemological states are all there is is not related at all.
So B might observe that itself and A have found C to be in state c_1 while A might find that B and itself have found C in state c_2. There is no paradox here of course.
But in this sense this complete "epistemologisation" of physics implies an extreme soliplism.

If we "synchronise" the different experiences we get something equivalent to collapse again.

In this sense it shows first and foremost that physical predictions are insensitive to the interpretation of Quantum Mechanics, but I wouldn't really call RQM an interpretaion of QM.

Now if A meassures what B has meassured with respect to C it will find it consistent with it's own meassurement of C. So will B with respect to A. What they will find if the epistemological states are all there is is not related at all.
So B might observe that itself and A have found C to be in state c_1 while A might find that B and itself have found C in state c_2. There is no paradox here of course.

I think you're still thinking externally.

I think you're imagining "Okay, A did his experiment, and saw this". And "B did her experiment, and saw that". And you, from your external viewpoint, are comparing things.

But if you do things internally, it all works out. You perform an experiment in which A and B meet to compare notes.

It's (IMHO) easy to see that the formalism predicts the only possible outcome is that A and B agree on what they saw.

What I meant is that if there is a third system D asking A and B what they saw it will find that A and B saw the same thing, but the problem remains that what A saw might be different from what B saw, because what they saw has reality only with respect to themself and not with respect to D.

I don't see a mechanism in the formalism that does what you say. Could you elaborate?

I meant my post to counter your assertion that we have to add in something called "synchronization", and that it's equivalent to collapse.

I assert it's already in the formalism, and doesn't involve collapse.

Logically correct (that is basically also Patrick's position), f-h is trying to put in realism again by his synchronisation procedure (which of course I do appreciate ). Ah elaborating upon f-h's comment, suppose A and B observe an electron flying trough an SG apparatus with polarization in the z direction and psi_electron = a |up> + b |down>, then the state D observes is
a |up > | Asees up> | Bsees up> + b |down> | Asees down> | Bsees down> at least when you can assume that A,B are reliable persons. Then D sees A and B agree as is determined by the quantum *dynamics*. Now indeed, it could be that if A,B and D are doing sequentially this game (with sufficient time for causal communication) then it could be that at the N'th step A records up, B down, D sees A and B record up, A sees B record up. That is the price to pay if you give up realism and still is the reason why I reject this line of thought.

Quantum states are not physical objects: they exist only in our imagination.

well, I don't know about you but in my imagination it's the other way round - there exist no quantum states Quantum states are not actually observable, but is that so mysterious? Potentials (thermo, electromagn.) e.g. are (in most cases) also not observable, but still it's handy to work with them.

Yes I agreed with that. As I said, there is no paradox and D sees A and B agree. But in RQM what you just wrote down was the analysis of what D sees A see which a priori has nothing to do with what A sees, that's the "problem".

Yes I agreed with that. As I said, there is no paradox and D sees A and B agree. But in RQM what you just wrote down was the analysis of what D sees A see which a priori has nothing to do with what A sees, that's the "problem".

Nice way to put it. Everybody always hears what they must hear to avoid paradoxes in RQM. You have to consider what "A sees B see" as independent from what "B sees" in the set up of your theory.

I basically answered that objection, each of your different relative states give different local ``collapse´´ possibilities. To synchronise these possibilities is tantamount to treating all macroscopic systems as classical which brings you back to the realist nonlocal collapses - that is exactly why I thought one year ago ``nonsense´´ when reading this (I am a realist, cannot help it).

The Rovelli paper makes it sound like some sort of gauge freedom -- I'm not sure what I think of that, but meh.

It's appealing to the theorem that it doesn't matter when wavefunction collapse is applied -- you'll get the same answers out either way. So it's reasonable to posit that the choice is aphysical (and that there is some aphysical freedom in the choice of wavefunction as well).

In other words, collapsing when A saw something, and then evolving to when D watches A and B compare notes is physically the same as just evolving all the way up until D's observation and collapsing there.